The invention relates to an inflatable airbag for an airbag unit having at least one tautening cord fastened to the vehicle body and operatively connected to the airbag, so that spread of the airbag during inflation is limited.
DE 196 54 490 A1 describes an airbag for a lateral airbag unit of preferably tube-like shape, said airbag being connected at least two points to the motor vehicle body and, in the uninflated state, being accommodated in a curved stowage space. Furthermore, between the airbag and a fastening point on the motor vehicle, at least one elongate tautening or tensioning element (designated hereafter as a tautening cord) is provided, which can be tautened when the airbag is inflated. The spread of the airbag during inflation is thereby limited.
Moreover, it is possible, by means of such a tautening cord, to prevent the situation where, in the event of a crash, vehicle occupants are thrown out of the vehicle through an open window or a window destroyed in the crash or where, after a crash, individual body parts of a vehicle occupant project through a window and therefore undergo the risk of correspondingly serious injury. For this purpose, however, it is necessary, in the event of a crash, for the tautening cord to remain tensioned even after the inflation of the airbag.
DE 197 07 347 A1 discloses an inflatable airbag for an airbag unit, with at least one tautening cord which can be fastened to a vehicle body and can be tautened during the inflation of the airbag and which limits the spread of the airbag during inflation. The tautening cord is operatively connected to the airbag in at least one region via a return stop (when the airbag unit is installed in a motor vehicle). As a result, during the inflation of the airbag, the tautening cord and the airbag can move relative to one another in a first direction in this region. After the inflation of the airbag, relative movement of the tautening cord and airbag in a second direction essentially opposite to the first direction is prevented. The return stop includes two wedges, one is a fixed wedge and is provided with grooves on its wedge face and the other is mounted movably by means of a tension spring. Although this return stop functions very reliably and safely, it nevertheless has a comparatively high weight and requires a corresponding large amount of space.
One problem on which the invention is based is to provide an inflatable airbag with a tautening cord of which remains in a tensioned state by simple means even after the inflation of the airbag.
This object is achieved, according to the invention, by the provision of an airbag for an airbag unit having a taunting cord fastened to a vehicle body. The taunting cord is operatively connected to the airbag to limit the spread of the airbag during inflation. The tautening cord is connected to the airbag so that during inflation the tautening cord and the airbag can move relative to one another in a first direction. After inflation, relative movement between the tautening cord and the airbag in a second direction generally opposite to the first direction is prevented.
There is provision for the tautening cord and the airbag to cooperate via at least one pair of adhesive faces and for the pair of adhesive faces to comprise two deformable face elements in the form of a hook face and of a counter-face. One of the faces is assigned to the airbag and the other to the tautening cord. The faces slide past one another during the relative movement in the first direction, while they come into engagement with one another during the relative movement in a second direction.
The airbag unit according to the invention can be implemented by cost-effective means. In addition, the airbag unit does not require the use of heavy parts which, in the event of a crash, could lead to injuries to a vehicle occupant.
A return stop may be formed by a pair of adhesive faces (in the manner of a touch-and-close fastening) which comprises two elastic deformable face elements in the form of a hook face and of a counterface.
The two face elements assigned to the airbag and to the tautening cord, may, in this case, have both a different reach and an identical reach in the direction of extent of the tautening cord. In one case, the face element assigned to the tautening cord may extend over a relatively long length, in particular essentially over the entire length of the tautening cord, in order to ensure a reliable engagement of the two face elements during a return movement.
According to one alternative of the invention, there is provision for the hooks of the hook face to run at an inclination to the counterface in such a way that they slide over the counterface during the relative movement in the first direction, while they engage into the counterface during the relative movement in the second direction.
According to another alternative of the invention, a sliding element runs between the hook face and the counterface. The sliding element allows for a relative movement of the two face elements. The sliding element may include an abutment on which one of the face elements acts during a relative movement in the second direction (return movement after the inflation of the airbag), in such a way that the sliding element is deformed and the two face elements (hook face and counterface) can come into engagement with one another.
Preferably, when the airbag is in the folded state, the sliding element lies, in the vicinity of its abutment, on the face element assigned to the tautening cord. During the inflation of the airbag, the face element assigned to the tautening cord can be guided behind the sliding element. During the return movement after the inflation of the airbag, the face element assigned to the tautening cord can run onto the abutment of the sliding element.
The sliding element itself is preferably a sliding sleeve which surrounds the tautening cord and has an abutment which makes it easier for the sliding element to experience deformation.
The return of the tautening cord after the inflation of the airbag is prevented in a particularly reliable way if the tautening cord has arranged on it two face elements, of which the surfaces provided with adhesive elements face in opposite directions and which are each assigned a face element on the airbag. The surface of the airbag may be provided with a pocket, in which the face elements assigned to the airbag are arranged and in which that portion of the tautening line which is provided with the face element extends.
When the tautening cord is firmly connected to the airbag at a point on the latter and is operatively connected to said airbag at a distance from this point, in another region, via the above-explained return stop (that is to say, for example, via a pair of adhesive faces), then, during inflation, the airbag can be tautened by means of the tautening cord between said fastening point and the return stop, the return stop ensuring that the tension of the tautening cord and of the airbag is maintained even after the inflation of the airbag.
According to the present invention, the tautening cord remains tensioned even after the inflation of the airbag. Thus, it may become difficult (in the case of a lateral or side airbag) for a vehicle occupant to open the vehicle door or even to leave the vehicle through a side window after an accident. Rescue work, in which there is to be access to the vehicle through a vehicle door or a window, may be impeded as a result.
In order to eliminate these disadvantages, the tautening cord includes a means for removing the tension from the tautening cord.
There may be provision for the tautening cord or a fastening means, which serves for fastening the tautening cord, to have a weakening region. The weakening region can withstand the forces occurring during the inflation of the airbag but also removes the tension from the tautening cord when specific predeterminable forces are exerted. The weakening region may be designed, as a predetermined breaking point which breaks when a defined force is applied.
In order to form the predetermined breaking point, for example, the tautening cord may be perforated or may consist of two parts which are connected to one another via a further structural element provided with a predetermined breaking point. Finally, the predetermined breaking point may also be provided in a fastening element for connecting the tautening cord to the airbag or to the vehicle body.
Instead of a weakening region being provided, a releasable fastening means may be used. The fastening means is used to connect the tautening cord to the vehicle body or for connecting two parts of the tautening cord to one another. This fastening means is released after a crash, in order to remove the tension from the tautening cord. A suitable releasable fastening means is, for example, a touch-and-close fastening.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.